1. Field of the Invention
This disclosure relates to a wheelchair apparatus capable of climbing and negotiating stairways and curbs.
2. Description of the Related Art
There has long been an interest in wheelchairs capable of climbing stairs and curbs as a means of imparting greater mobility, and hence self-sufficiency, to wheelchair-bound persons. During the 1950s and 1960s, a design contest sponsored by the National Inventors Council and the President's Committee on the Employment of the Physically Handicapped generated significant interest among inventors in stair-climbing wheelchairs. The contest was established in recognition of the fact that no practical stair-climbing wheelchair existed.
Examples of designs developed during this period are shown in U.S Pat. No. 3,226,128 to Grier and U.S Pat. No. 3,269,478 to Joslyn.
Grier discloses fore and aft skids attached to chair drive wheel axles interior to the wheels. A gripping means holds the chair on the stairs while the skids move the chair up the stairs, wherein the skids rest on the nose of a given step at intervals. Grier's design is susceptible to slippage and often puts the operator in various unstable positions involving precarious balance of the chair.
Joslyn discloses a chair comprising a pair of vertically-oriented, hydraulically-operated lifting legs fore and aft on each side of the chair. The legs are interconnected and are pivoted at on the chair at their top ends. The cylinders lift the chair up a stair, and the operation is repeated until the chair negotiates the stairs. The lifting apparatus is relatively large and awkward and must be attached exterior to the wheels, resulting in a wheelchair that is extra wide and thus of limited utility.
More recent examples of stair-climbing wheelchairs include the iBOT Mobility System, an electronic stair-climbing wheelchair which has received FDA approval. See http://www.ibotnow.com. Although the iBOT Mobility System offers significant advantages over previous designs, it is expensive and thus not a feasible option for a large percentage of wheelchair-bound individuals.
Currently known designs of stair-climbing wheelchairs can be grouped into electrically-powered and human-powered chairs. Electrically-powered stair-climbing wheelchairs generally comprise batteries, an electric motor, controllers, and/or various actuators, resulting in an expensive and heavy apparatus that is generally unavailable to those without significant financial resources. Human-powered stair-climbing wheelchairs generally comprise a large number of moving parts, resulting in a complicated apparatus that is difficult to maintain and transport.
Thus there exists a significant need for a light, simple, durable stair-climbing wheelchair with relatively few moving parts involved in the stair-climbing mechanism.